1. Field of the Invention
The present invention relates to a substrate treatment method. More particularly, the present invention is related to a substrate treatment method by single wafer processing using a chemical liquid.
2. Description of Related Art
In a wet process (e.g., surface cleaning, oxide etching, and resist removal) of the semiconductor fabrication process, a surface treatment using a rotary, single wafer processing apparatus is conducted. Specifically, a wafer is held by a holding member set in a processing chamber of the single wafer processing apparatus, and the holding member is spun. Then, a chemical liquid, such as diluted hydrofluoric acid (DHF) or sulfuric acid (H2SO4)/H2O2, is fed to the wafer at a portion close to the spin center from a nozzle arranged above the holding member. The chemical liquid flows on the wafer in the direction to the outer periphery due to a centrifugal force, thus achieving a desired surface treatment. After completion of the surface treatment, the wafer is cleaned by feeding pure water to the wafer surface to remove the chemical liquid component.
It has been known that the cleaning treatment of the wafer using pure water has the following problem. Since pure water has a resistivity as large as 18 MΩ·cm, in an area of the wafer surface to which the pure water is fed, when this area touches the pure water, static electricity is generated due to the friction of the pure water against the wafer, so that the wafer surface is locally charged. For this reason, there occur troubles such as breaking of a gate oxide film or dissolving of a metal film constituting a wiring or electrode. For solving the problem, an attempt has been made to add carbon dioxide (CO2) gas or ammonia (NH3) gas to pure water to lower the resistivity of the pure water, thereby preventing the wafer from being charged (see, for example, Japanese Patent Application Publication (KOKAI) No. 2002-373879).
On the other hand, it has been known that a chemical liquid used in the above-mentioned wet process, particularly in the cleaning treatment of the wafer is ionized into ions and hence generally has a low resistivity. For example, SC1 (ammonia+hydrogen peroxide+water), which is a chemical liquid for removing organic substances on the wafer surface, or SC2 (hydrochloric acid+hydrogen peroxide+water), which is a chemical liquid for removing metals on the wafer surface, has a high ion concentration. Therefore, an area of the wafer surface to which such a chemical liquid is fed is unlikely to be charged when the area touches the chemical liquid.